Pinterest Authentication Failed

Hi,
we need to implement "Pinterest Authentication" in xamarin forms. we have used below code :

void LoginToPinterest ()
{
var auth = new OAuth2Authenticator (
clientId : "1442181",
clientSecret : "a6b3c1d5",
scope : "read_write", //"read", // read_write
authorizeUrl : new System.Uri ("https://pinterest.com/oauth/authorize/"),
redirectUrl : new System.Uri ("https://www.socialphoto.com"),
accessTokenUrl : new System.Uri ("https://pinterest.com/oauth/access_token/")
);
auth.AllowCancel = true;
auth.Completed += async delegate(object sender, AuthenticatorCompletedEventArgs e) {
if(e.IsAuthenticated)
{
}
DismissViewController (true, null);
App.SuccessfulLoginAction.Invoke ();
};
UIViewController vc = auth.GetUI ();
PresentViewController (vc, true, null);
}
Above code showing error when Authentication popup is display : http://screencast.com/t/vBKaxLDMKXvm